Transportation system

ABSTRACT

A transportation system having a roadway and a plurality of vehicles movable over the roadway, the roadway having parallel guide rails between which the vehicles move, the vehicles having pairs of front and rear wheels which are turned as required by individual guide and steering means engageable with the guide rails for guiding movement of the vehicles along each section of the track and for selectively steering or switching the vehicles from one section of the roadway to another which extends angularly therefrom.

United States Patent [191 Nelson May 28, 1974 1 1 TRANSPORTATION SYSTEM[75] Inventor: Roy A. Nelson, Grand Prairie, Tex.

[73] Assignee: LTV Aerospace Corporation, Dallas,

Tex.

[22] Filed: Oct. 13, 197.2

[21] Appl. No.: 298,716

[52] US. Cl 104/130, 105/215 R, 104/24 S [51] Int. Cl B611) 5/02 [58]Field of Search....... 104/130, 96, 105, 88, 242,

[56] References Cited UNlTED STATES PATENTS 3,119,349 1/1964 Hampton104/130 3,643,601 2/1972 Taylor 104/88 3,650,216 3/1972 Broome 104/130 XPrimary ExaminerM. Henson Wood, Jr.

Assistant Examiner-D. W. Keen Attorney, Agent, or FirmWalter J. Jagmin;H. C. Goldwire; James M. Cate [5 7] ABSTRACT 13 Claims, 6 DrawingFigures iATENTEDm 28 I974 SHEET 1 OF 4 mmm 1 TRANSPORTATION SYSTEM Thisinvention relates to transportation systems and more particularly totransportation systems having vehicles movable over a roadway of thesystem and to vehicles having guide and steering means for guiding andsteering the vehicles during their movement over the roadway.

An object of this invention is to provide a new and improvedtransportation system having a roadway and vehicles movable thereover.

Another object is to provide a transportation system, of the typedescribed wherein the roadway has a main section and at least one shuntsection extending angularly from the main section, the sections of theroadway having parallel side guide rails and the vehicles having guideand steering wheels selectively engageable with the guide rails of theroadway sections for guiding the movement of the vehicles over eachsection and steering it from one section onto another as desired.

Still another object is to provide a transportation system, of the typedescribed, which has switch means located along the roadway forselectively operating the steering wheels of the vehicles to cause themto move along desired sections of the roadway.

An important object of the invention is to provide a new and improvedvehicle which has pairs of front and rear wheels and individual guideand steering means operatively associated with each pair of wheelscooperable with the guide rails of the system for guiding and steeringthe vehicle as it moves over the roadway of a transportation system.

Other objects and advantages will be apparent from the specification andclaims and from the accompanying drawing illustrative of the invention.

In the drawing:

FIG. 1 is a top view of the chassis of a vehicle of the transportationsystem embodying the invention on the roadway thereof;

FIG. 2 is a front view of the system illustrated in FIG.

FIG. 3 is a side view, with some parts shown in section and some brokenaway, of the system illustrated in FIG. 1;

FIG. 4 is an enlarged sectional view taken on line 4-4 of H6. 1;

FIG. 5 is an enlarged sectional view taken on line 5-5 of FIG. 1; and,

FIG. 6 is a schematic top view of a portion of the transportation systemembodying the invention.

Referring now to the drawings, the transportation system T embodying theinvention includes a roadway R along whose top planar surface travelvehicles V of the system. The road may have several sections such as S1and S2 and includes side tracks or guide rails such as 12 and 13b whichdefine the main section S1 of the roadway and guiderails l4 and 15 whichdefine a shunt section S2 of the roadway which curves away from the mainsection intermediate ends thereof. The guide rail 15 is connected to theguide rail 13a -by a curved guide rail 16 and the guide rail 14 isconnected to the guide rail 13b by a curved guide rail 16. Switch rampassemblies l8 and 19 whose function will be explained below are providedupstream of the intersection of the two sections.

Each of the vehicles V has a chassis 20 which includes a pair oflongitudinally extending frame mem- 2 bers 21 and 22 connected at theirfront and rear ends by a pair of transverse members 23 and 24 and byintermediate transverse members 24a and 24b. The chassis at its rightrear corner has a kingpin housing 25 whose bracket 26 is connected bymeans of bolts 27 to the bracket 28 on the outer end of the horizontalarm 29 of the vertical comer post 30 of the chassis.

The right rear comer of the chassis is supported by a wheel 32 mountedfor rotation on the horizontal axle 33 rigid with and extendinghorizontally from the vertical kingpin 34. The kingpin extends rotatablyand vertically slidably through the housing 25 and the top and bottombearings 36 and 37 mounted in the housing. Downward movement of thehousing, and therefore of the right rear chassis corner, relative to thekingpin is yieldably resisted by a spring 38 whose upper end bearsagainst the top bearing and whose bottom end bears against the upwardlyfacing shoulder 39 of an external annular flange 40 of the kingpin.

The other corners of the chassis are supported by wheels 32a, 32b and32c which are connected to the left rear, left front, and right frontchassis corners in the same manner as the wheel 32 is connected to thechassis right rear corner, and, accordingly, the elements of the meansby which the wheels 32a, 32b, and 32c are connected to the chassis havebeen provided with the same reference characters, to which thesubscripts a, b and. c, respectively, have been added, as thecorresponding elements of the means by which the wheel 32 is connectedto the chassis right rear corner.

The kingpins 34 and 34a of the rear pair of wheels are connected by theusual tie rod linkage 44 which includes a transverse rod 45 whoseopposite ends are pivotally connected, as at 46 and 46a, to the innerends of the arms 47 and 47a of the kingpins 34 and 34a, respectively.The kingpin arms extend horizontally forward, then upwardly andforwardly and then transversely inwardly to clear the wheels 32 and 32aand the chassis 20.

The front wheels 32b and 32c are similarly connected by a tie rodlinkage 50 which includes a transverse rod 51 pivotally connected, as at52 and 53, to the arms 47b and 470 of the kingpins 34b and 34c.

It will be apparent, therefore, that the wheels of each pair of frontand rear wheels will turn simultaneously and to a corresponding degreeabout the vertical axes of their respective kingpins.

The rear pair of wheels are steered by a guide and steering assembly 60connected to the bottom ends of the kingpins 34 and 34a. The assembly 60includes a bracket 62 having a vertical bore 63 in which is telescopedand rigidly secured, as by welding, the bottom end portion of thekingpin 34 below the axle 33.

A wheel mount assembly 65 is supported by the bracket 62 and has a mountbracket 66 comprising rear and front plates 67 and 68 between and towhich are rigidly secured shaft blocks 69 and 70 in any suitable manner,as by welding. The wheel mount assembly 65 is vertically movably securedto the kingpin bracket 62 by a pair of parallelogram arms or links 71and 72 pivotally connected to the bracket 62 by bolts 73 which extendthrough aligned apertures in the rear ends of the links and the verticalflanges 74 and 75 of the bracket 62. The front ends of the links aresimilarly pivotally secured to the mount assembly plate 67 by bolts 76which extend through aligned apertures in the top and 3 bottom pairs oflugs 77 extending rearwardly from the plate 67.

The mount assembly is yieldably supported by a leaf spring 80 whose rearend extends between the pair of lugs 81 of the brackets 62, and may besecured I axle or shaft 84 secured to the shaft block 70 and is adaptedto engage the web of the guide tracks 13b, 17 and 14. An outer steeringwheel 85 is rotatably mounted on a shaft 86 which is vertically slidablein the bearing block 69 and which has lower and top stops 87 and 88engageable with the bearing block to limit vertical movement of theshaft and wheel 85 relative to the plates 67 and 68.

The lower stop 87 extends rearwardly of the rear plate and has securedthereto a rod 89 whose upper end telescopes slidably into a sleeve 90rigidly secured to the rear plate 67 in any suitable manner, as bywelding. One end of a cable 91 is secured to the top end of the rod 89and extends slidably through a flexible sheath 92 which is secured tothe top end of the sleeve 90.

The guide and steering assembly 60 also includes a wheel mount assembly65a which is connected to the kingpin 34a in the same manner as thewheel mount 65 and, accordingly, elements of the wheel mount.assembly65a have been provided with the same reference numerals to which thesubscript a has been added, as the elements of the wheel mount assembly65.

The other end of the cable 91 is secured to a rod 89a mounted on thestop 87a which is telescoped in a sleeve 90a and the other end of thesheath 92 is secured to the sleeve90a of the wheel mount assembly 6511.Due to the provision of the cable or wire 91 whose movement isrestrained by the sheath 92, when one of the steering wheels, forexample, the steering wheel 85, is moved upwardly, the other steeringwheel 85a will be moved downwardly and vice versa for a purpose to bedescribed below.

The front wheels 32b and 32c are similarly guided and steered by a guideand steering assembly which is identical to the guide and steeringassembly 60 of the rear wheels and, accordingly, its elements have beenprovided with the same reference numerals, to which the prefix 1 hasbeen added, as the corresponding elementsof the guide and steeringassembly 60.

The guide wheels 83 and 183 of the wheels 32 and 32c are engageable withthe vertical web of the l-beam guide rails 13b, 17 and 14, or 13b and13a, between their inner flanges 201 and 202, and, similarly the innerguide wheels83a and 1830 of the left wheels 32a and 32b are engageablewith the vertical web of the guide track 12 between its inner flanges203 and 204.

Upstream of any shunt section of the roadway, such as the shunt sectionS2, portions of the top external flanges 205 and 206 of the guide rails12 and 13b are ,removed at the locations of switching assemblies 18 and19, respectively, in order to permit vertical displacement of thesteering wheels by the switch assemblies 18 and 19.

The switch assembly 18 includes a ramp member 210 which is pivotallysecured, as at 211, to a housing 212 embedded alongside the roadway. Theramp 210 is pivotable between the full line position and the broken lineposition, illustrated in F l6. 3, by an electric motor 214 suitablymounted in the housing 212 whose drive shaft 215 has eccentricallymounted thereon a circular cam 216. A drive rod 218 has its forward endpivotably connected, as at 219, to the dependent arm 220 of the ramp 210and its other end is secured to a cam follower 221 whose hub 222 istelescoped on the cam 216..

It will be apparent that when the drive shaft 215 is rotated degreesfrom the position illustrated in FIG. 3, the switch ramp 210 is pivotedfrom the full line position to the broken line position in acounterclockwise manner about the axis of its pivotal connection 211 tothe housing and when it is rotated through an additional 180, the rampis rotated back to the full line position illustrated in FIG. 3. Theramp 210 when it is moved to its raised shunting or switching position,inclines upwardly and forwardly to engage the steering wheels 185 andthen 85 as the vehicle moves forwardly and moves first the frontsteering wheel 185 and then the rear steering wheel 85 upwardly at thelocations of the gaps in the outer flanges of the guide rail 13b.Simultaneously with such upward movement of the steering wheels 185 and85, the left steering wheels 185a and 85a are moved downwardly topositions wherein they will engage the outer surface of the web of theguide rail 12. The drive shaft 214 of the motor shaft 214 extendsthrough a suitable transverse passage 230 below the roadway and isjournaled at its end remote from the motor 214 in a suitable pillowblock 233.

The switching assembly 19 includes a switching ramp 2100 which is drivenby a cam 216a in the same manner as the switch ramp 210 and,accordingly, the elements of the switching assembly 19 have beenprovided with the same reference numerals, to which the subscript a hasbeen added, as the corresponding eiements of the switch assembly 18. Thecam 2160 is displaced 180 from the orientation of the cam 216 so thatthe switch ramp 210a is in its raised operative position when the switchramp 210 is in its lower operative position and vice versa.

The chassis has a carriage C connected thereto by suitable linkages 241,242, and 243 which provide for vertical adjustment of a secondary 244 ofa linear induction motor whose primaries P are embedded in the roadwayand by pins 245 and 246 of the carriage which extend vertically upwardlyand slidably into chassis brackets 247 and 248, respectively. Since themounting means of the secondary 244 and details of the structure of thecarriage C are not claimed in this application, they will not bedescribed in greater detail herein but are fully described in theapplication of Roy A. Nelson being filed concurrently with the tiling ofthis application and assigned to the same assignee.

Assuming now that the vehicle V1 is moving in the direction indicated bythe arrow in FIG. 6 along the main section S1 of the roadway, andapproaches the location of the switch assemblies 18 and 19, if thevehicle is to be switched or shunted off to the shunt section S2 of theroadway, the motor 214 is energized by a suitable control means, nowshown, so as to move the ramp 210a to its upper position illustrated inH6. 2 and the ramp 210 will be moved to its lower position illustratedin FIG. 3. As the vehicle moves forwardly, the front left steering wheel185a will be engaged by the ramp 210a and will be moved upwardly abovethe outer flange 204 of the guide rail 12. Such upward motion of thesteering wheel 185a will cause downward movement of the steering wheel185 and, the front wheels 32b and 32c will be turned in clockwisedirections about the axes of their kingpins 34b and 340 as the steeringwheel 185 engages first the web of the guide rail 13b, then the web ofthe guide rail 17 and finally the web of the guide rail 14 as thevehicle moves forwardly. Similarly as the steering wheel 85a moves pastthe switch ramp 210a, it will be raised above the guide rail 12 whilethe right rear steering wheel 85 is lowered to position to engage thewebs of rhe guide rails 13b, 17 and 14 as the vehicle moves forwardly.

Once the right steering wheels move past the switch assembly 18, theymove below the top external flange of the guide rails 13b, 17 and 14which then prevents accidental upwardly displacement of the rightsteering wheels.

If it has been desired to cause the vehicle Vl to continue to moveforwardly in a straight line along the main section S1 past the shuntsection S2, the ramp 210 would have been raised while the ramp 210awould have been lowered so that the engagement of the right steeringwheels 185 and then 85 therewith would have caused the right steeringwheels to be raised to inoperative position above the guide rail 13b andthe left steering wheels 185 and then 85a to be lowered to theiroperative positions below the external top flange of the guide rail 12.As a result the vehicle would then move forwardly from between the rails12 and 13 to between the guide rails 12 and 13a and will not turn intothe shunt section S2.

The operation of the motor 214 may of course be controlled by anysuitable controls located either remote from the roadway or on thevehicle itself or alternatively a suitable mechanical means could beemployed on the vehicle to move the steering wheels vertically asdesired to cause proper switching of the vehicles to a shunt track or topermit them to move forwardly along the main section S1 instead ofshunting over to the section S2. Such controls may also include limitswitches such as the switch 250, FIG. 3, engageable by the switch rampto deenergize the motor 214 whenever the ramps are moved to either oftheir two extreme positions.

It will be apparent that the vehicles are propelled along the roadway bya linear induction motor which includes the primaries P embedded, in theroadway, whose windings are energized by three phase alternatingcurrent, and the secondary 244 mounted on the carriage C of the vehicle.Other drive or propelling means could, of course, be used to drive thevehicles over the roadway such as that disclosed in the pendingapplication of Roy A. Nelson, Ser. No. 258,701 filed June 1, 1972 forTransportation System.

It will also be apparent that the inner guide wheels, such as the guidewheels 83 and 83a of the rear wheels and 183 and 183a of the frontwheels, guide movement of the vehicles along portions of the roadwaybetween locations of intersections of two sections thereof, such assections S1 and S2.

Due to the mounting of the wheel mount assemblies 65, 65a, 165 and 165ato the kingpins of the wheels 32,

'32a, 32c and 32b, respectively, by the parallelogram links, the wheelmount assemblies may move vertically without causing any tilting of theaxes of rotation of the guide and steering wheels. The yieldable supportof these wheel mount assemblies by the leaf springs permits them to movevertically if the guide rails are displaced vertically from the surfaceof the roadway as at locations where the roadway intersects other roadsalong which automobiles or the like travel. At such 10- cations theguide rails may be lowered below the top surface of the roadway R andthe guide and steering wheels would then be pushed downwardly as theyengaged the top flanges of the guide rails as they moved into thedownwardly curved portions, as at 230, FIG. 3, of the guide railsagainst the resistance of the leaf springs 80.

It will now be seen that a new and improved transportation system hasbeen illustrated which includes a roadway having one or more sectionswhich extend angularly from one another at intersections thereof andwith each section having vertical parallel side guide rails and thevehicle having individual guide and steering means for its rear and itsfront wheels cooperable with the guide rails for turning the pairs ofwheels as required to cause it to travel in a desired course over theroadway.

It will also be seen that the roadway may have associated therewithswitch means for selectively operating the guide and steering means ofthe pairs of wheels of the vehicle to cause the vehicle to turn from onesection of the roadway to another section.

It will further be seen that a newand improved vehicle has beenillustrated and described which has guide and steering means cooperablewith parallel vertical side guide rails of a roadway'for controlling thedirection of movement of the vehicle over the roadway.

It will further be seen that the wheel mount assemblies 65, 65a, and165a are positioned forwardly of the wheels which they guide and steerso that the wheels are caused to start turning as they approach a shuntsection to move properly thereonto.

While only one embodiment of the invention, together withmodificationsthereof, has been described in detail herein and shown inthe accompanying drawing, it will be evident that various furthermodifications are possible in the arrangement and construction of itscomponents without departing from the scope of the invention.

What is claimed is:

l. A vehicle for travel over a roadway of a transportation system, theroadway having a main section and at least one shunt section extendingangularlyfrom the main section, each section having parallel guide railsat the sides thereof extending upwardly therefrom, at least one rail ofthe shunt section connecting to one rail of the main section at thelocation of connection of the two sections, said vehicle including:

a chassis;

a pair of rear wheels supporting the rear end of the chassis and a pairof front wheels supporting the front end of the chassis, said wheelsbeing rotatable about horizontal axes and turnable about vertical axes;

separate tiemeans connecting the wheels of each pair of front and rearwheels for causing the wheels of each pair of wheels to turnsimultaneously; and

separate guide and steering means connected to each pair of wheels andoperatively associated with the guide rails for guiding said wheelsalong each section of the roadway and for steering the wheels forswitching movement of the vehicle from one section of the roadway toanother, each of said wheels being mounted on a kingpin turnable about avertical axis and each guide and steering means including;

separate wheel mount assembly connected to the kingpin of each wheel ofa pair of the vehicle wheels, each wheel mount including a bracket, aguide wheel mounted on the bracket for rotation about a vertical axisand engageable with inner vertical surfaces of an adjacent guide railand a steering wheel mounted on said bracket for limited verticalmovement between a lower operative position wherein it is engageablewith the outer vertical surface of the adjacent guide rail and an upperinoperative position wherein it is above the guide rail, said steeringwheel being rotatable about a vertical axis; and

separate means interconnecting the steering wheels of each pair ofsteering wheels for causing one steering wheel of the pair to move toits lower operative position when the other steering wheel of the pairis moved to its upper inoperative position.

2. The vehicle of claim 1, wherein said bracket of each wheel mountassembly is spaced forwardly and connected to its associated kingpin bylinkage means providing for vertical movement of said brackets relativeto said kingpin.

3. The vehicle of claim 2, wherein said bracket of each wheel mountassembly is yieldably held against downward movement.

4. The vehicle of claim 3, wherein said means interconnecting saidsteering wheels includes a flexible member extending between said wheelsand a sheath confining said flexible member, opposite ends of saidflexible member being connected to the wheels for vertical movementtherewith.

5. The vehicle of claim 1, wherein said means interconnecting saidsteering wheels includes a flexible member extending between said wheelsand a sheath confining said flexible member, opposite ends of saidflexible member being connected to the wheels for vertical movementtherewith.

6. A transportation system including:

a roadway providing a substantially horizontal support surface, saidroadway comprising a main section and at least one shunt sectionconnected to and extending angularly from the main section;

parallel guide rails at the sides of each section of the roadway and acurved guide rail connecting adjacent ends of the guide rails of themain and shunt section at the location of connection of the shuntsection to the main section at the side of the main section from whichsaid shunt section extends angularly outwardly;

said guide rails having top inner and outer horizontal flanges, saidouter flanges of the main section having slots therein at locationsspaced from the location of connection of the shunt section to the mainsection; and a vehicle including:

a chassis;

a pair of rear wheels supporting the rear end of the chassis and a pairof front wheels supporting the front end of the chassis, said wheelsbeing rotatable about horizontal axes and turnable about vertical axes;separate tie means connecting the wheels of each pair of front and rearwheels for causing the wheels of each pair of wheels to turnsimultaneously; separate guide and steering means connected to each pairof wheels and operatively associated with the guide rails for guidingsaid wheels along each section of the roadway and for steering thewheels for switching movement of the vehicle from one section of theroadway to another, each wheel being mounted on a kingpin turnable abouta vertical axis and each guide and steering means including: separatewheel mount assembly connected to the kingpin of each wheel of a pair ofthe vehicle wheels, each wheel mount including a bracket, a guide wheelmounted on the bracket for rotation about a vertical axis and engageablewith inner vertical surfaces of an adjacent guide rail and a steeringwheel mounted on said bracket for limited vertical movement between alower operative position wherein it is engageable with the outervertical surface of the adjacent guide rail and an upper inoperativeposition wherein it is above the guide rail, said steering wheel beingrotatable about a vertical axis; and

separate means interconnecting the steering wheels of each pair ofsteering wheels for causing one steering wheel of the pair to move toits lower operative position-when the other steering wheel of the pairis moved to its upper inoperative position.

7. The transportation system of claim 6, wherein said bracket of eachwheel mount assembly is spaced forwardly and connected to its associatedkingpin by linkage means providing for vertical movement of saidbrackets relative to said kingpin.

8. The transportation system of claim 7, wherein said bracket of eachwheel mount assembly is yieldably held against downward movement.

9. The transportation system of claim 8, wherein said meansinterconnecting said steering wheels includes a flexible memberextending between said wheels and a sheath confining said flexiblemember, opposite ends of said flexible member being connected to thewheels for vertical movement therewith.

10. The transportation system of claim '9, and switch means for movingone steering wheel of a pair of steering wheels upwardly and the otherdownwardly at the locations of slots in the outer top flanges.

11. The transportation system of claim 10, wherein said switch meanscomprise switch ramp pivotally mounted below said slots and movablesimultaneously between operative and inoperative positions wherein oneramp is in its operative position extending upwardly and forwardly inthe direction of movement of the vehicle and in position to engage asteering wheel of a vehicle and move it upwardly of the adjacent outerflange and the other switch ramp is in a lower inoperative position.

12. The transportation system of claim 6, wherein said meansinterconnecting said steering wheels includes a flexible memberextending between said wheels and a sheath confining said flexiblemember, opposite ends of said flexible member being connected to thewheels for vertical movement therewith.

13. The transportation of claim 12, and switch means for moving onesteering wheel of a pair of steering wheels upwardly and the otherdownwardly at the locations of slots in the other top flanges.

1. A vehicle for travel over a roadway of a transportation system, theroadway having a main section and at least one shunt section extendingangularly from the main section, each section having parallel guiderails at the sides thereof extending upwardly therefrom, at least onerail of the shunt section connecting to one rail of the main section atthe location of connection of the two sections, said vehicle including:a chassis; a pair of rear wheels supporting the rear end of the chassisand a pair of front wheels supporting the front end of the chassis, saidwheels being rotatable about horizontal axes and turnable about verticalaxes; separate tie means connecting the wheels of each pair of front andrear wheels for causing the wheels of each pair of wheels to turnsimultaneously; and separate guide and steering means connected to eachpair of wheels and operatively associated with the guide rails forguiding said wheels along each section of the roadway and for steeringthe wheels for switching movement of the vehicle from one section of theroadway to another, each of said wheels being mounted on a kingpinturnable about a vertical axis and each guide and steering meansincluding; a separate wheel mount assembly connected to the kingpin ofeach wheel of a pair of the vehicle wheels, each wheel mount including abracket, a guide wheel mounted on the bracket for rotation about avertical axis and engageable with inner vertical surfaces of an adjacentguide rail and a steering wheel mounted on said bracket for limitedvertical movement between a lower operative position wherein it isengageable with the outer vertical surface of the adjacent guide railand an upper inoperative position wherein it is above the guide rail,said steering wheel being rotatable about a vertical axis; and separatemeans interconnecting the steering wheels of each pair of steeringwheels for causing one steering wheel of the pair to move to its loweroperative position when the other steering wheel of the pair is moved toits upper inoperative position.
 2. The vehicle of claim 1, wherein saidbracket of each wheel mount assembly is spaced forwardly and connectedto its associated kingpin by linkage means providing for verticalmovement of said brackets relative to said kingpin.
 3. The vehicle ofclaim 2, wherein said bracket of each wheel mount assembly is yieldablyheld against downward movement.
 4. The vehicle of claim 3, wherein saidmeans interconnecting said steering wheels includes a flexible memberextending between said wheels and a sheath confining said flexiblemember, opposite ends of said flexible member being connected to thewheels for vertical movement therewith.
 5. The vehicle of claim 1,wherein said means interconnecting said steering wheels includes aflexible member extending between said wheels and a sheath confiningsaid flexible member, opposite ends of said flexible member beingconnected to the wheels for vertical movement therewith.
 6. Atransportation system including: a roadway providing a substantiallyhorizontal support surface, said roadway comprising a main section andat least one shunt section connected to and extending angularly from themain seCtion; parallel guide rails at the sides of each section of theroadway and a curved guide rail connecting adjacent ends of the guiderails of the main and shunt section at the location of connection of theshunt section to the main section at the side of the main section fromwhich said shunt section extends angularly outwardly; said guide railshaving top inner and outer horizontal flanges, said outer flanges of themain section having slots therein at locations spaced from the locationof connection of the shunt section to the main section; and a vehicleincluding: a chassis; a pair of rear wheels supporting the rear end ofthe chassis and a pair of front wheels supporting the front end of thechassis, said wheels being rotatable about horizontal axes and turnableabout vertical axes; separate tie means connecting the wheels of eachpair of front and rear wheels for causing the wheels of each pair ofwheels to turn simultaneously; separate guide and steering meansconnected to each pair of wheels and operatively associated with theguide rails for guiding said wheels along each section of the roadwayand for steering the wheels for switching movement of the vehicle fromone section of the roadway to another, each wheel being mounted on akingpin turnable about a vertical axis and each guide and steering meansincluding: a separate wheel mount assembly connected to the kingpin ofeach wheel of a pair of the vehicle wheels, each wheel mount including abracket, a guide wheel mounted on the bracket for rotation about avertical axis and engageable with inner vertical surfaces of an adjacentguide rail and a steering wheel mounted on said bracket for limitedvertical movement between a lower operative position wherein it isengageable with the outer vertical surface of the adjacent guide railand an upper inoperative position wherein it is above the guide rail,said steering wheel being rotatable about a vertical axis; and separatemeans interconnecting the steering wheels of each pair of steeringwheels for causing one steering wheel of the pair to move to its loweroperative position when the other steering wheel of the pair is moved toits upper inoperative position.
 7. The transportation system of claim 6,wherein said bracket of each wheel mount assembly is spaced forwardlyand connected to its associated kingpin by linkage means providing forvertical movement of said brackets relative to said kingpin.
 8. Thetransportation system of claim 7, wherein said bracket of each wheelmount assembly is yieldably held against downward movement.
 9. Thetransportation system of claim 8, wherein said means interconnectingsaid steering wheels includes a flexible member extending between saidwheels and a sheath confining said flexible member, opposite ends ofsaid flexible member being connected to the wheels for vertical movementtherewith.
 10. The transportation system of claim 9, and switch meansfor moving one steering wheel of a pair of steering wheels upwardly andthe other downwardly at the locations of slots in the outer top flanges.11. The transportation system of claim 10, wherein said switch meanscomprise switch ramp pivotally mounted below said slots and movablesimultaneously between operative and inoperative positions wherein oneramp is in its operative position extending upwardly and forwardly inthe direction of movement of the vehicle and in position to engage asteering wheel of a vehicle and move it upwardly of the adjacent outerflange and the other switch ramp is in a lower inoperative position. 12.The transportation system of claim 6, wherein said means interconnectingsaid steering wheels includes a flexible member extending between saidwheels and a sheath confining said flexible member, opposite ends ofsaid flexible member being connected to the wheels for vertical movementtherewith.
 13. The transportation of claim 12, and switch means formoving one steering wheel of a pair of steering wheeLs upwardly and theother downwardly at the locations of slots in the other top flanges.